Communication devices, such as radiotelephones, are being developed for users to wear on their wrists, around their waists and in their pockets. Primary antennas that protrude from these devices may be undesirable because they may interfere with a user's comfort. Furthermore, because of the relative closeness of a primary antenna to a user's body, radio frequency (RF) signals may be blocked. Also, conventional primary antennas may not radiate outwardly with sufficient gain to overcome the close proximity of a user. Accordingly, radiotelephones may not function properly when in close proximity to a user during operation.
Primary antennas for radiotelephones may not function adequately when a user is moving during operation of the radiotelephone. Close proximity to objects or movement of a user during operation of a radiotelephone may result in degraded signal quality or fluctuations in signal strength, known as multipath fading. Diversity antennas have been designed to work in conjunction with a radiotelephone's primary antenna to improve signal reception and overcome multipath fading.
Radiotelephones and other communication devices are also undergoing miniaturization. Indeed, many of the contemporary models are less than 11-12 centimeters in length. Unfortunately, as radiotelephones decrease in size, the amount of internal space therewithin may be reduced correspondingly. A reduced amount of internal space may make it difficult for both primary antennas and diversity antennas contained within a radiotelephone to achieve the bandwidth and gain requirements necessary for radiotelephone operation because their size may be correspondingly reduced.
Furthermore, it may be desirable for a radiotelephone antenna to be able to resonate over multiple frequency bands. For example, the Japanese Personal Digital Cellular (PDC) system utilizes two "receive" frequency bands and two "transmit" frequency bands. Unfortunately, the ability to provide antennas with adequate gain over multiple frequency bands may be presently limited because of size limitations imposed by radiotelephone miniaturization.